The Arizona sentinel., 1887-06-18
CHEMISTRY OF SOAP.
Interesting Information Regarding It's
 Composition and Effects

Interesting Information Regarding us
 Composition and Effects
 That important article of household
 use, soap, is Of considerable interest
 from a chemical point of view. It is a
 true salt or compound of an acid and
 in which the acids occurring in fats,
 where they are combined with glycer-
 inc as base, are separated from it, and
 combined with the alkali soda or pot
 ash. Soaps in which the fatty acids
 are combined with lime, magnesia, lead
 or iron are also known, but are only used for medical purposes. The crys- talline salts of soda are, as general rule, efflorescent; that is, on exposure
 to the air they give off moisture, and
 crumble into dry powder. Potash salts, on the other hand, are oftener delinquescent
 absorbing moisture from the air, and becoming liquid. This is also true of the soaps made from these alkalies; hard soap being made from soda, and soft soap from potash. A good soap should be perfectly neutral. containing neither excess offatty acids or alkali. An excess of free alkali in a soap will increase its cleansing power, but has an injurious effect upon the skin and
 clothing. It is a common practice to
 add carbonate of soda to laundry soap
 for a similar purpose, but its can not
 be recommended. The cleansing &C., of fho of ho cofIc. factorily explained, but it is doubtless due to the alkal contained in it Probably some sort of double decom- position takes place between the soap and the greasy impurities of the skin or soiled linen, by which they are rendered soluble in water. Wash ing powders are almost always cont posed of carbonate of soda They may occasionally be of use in removing very obstinate spots, but their constant use causes the clothing to wear out very rapidly. Borax is less objection able, and may sometimes serve a good purpose as an auxiliary to the soap. Ammonia will often remove stains which are not affected by the ordinary cleansing process, but so powerful an agent should be used with care. The process of bluing illustrates an impor- tant law of color. Freshly washed linen is of a slightly yellowish tint, which appears to be an optical illusion dependingupon its excessive whiteness. Now. blue and yellow are complement ary colors; that is, when blue and yellow light are combined. white light is formed. So the addition of trace of blue color to the linen neu- tralizes the yellow tint, and renders it apparently perfectly white. Bluing is usually made from indigo, though Prussian blue, ultramarine and aniline blue are sometimes used The same process of bluing is applied to sugar to give it winter appearance. Starch is vegetable product usually pro- cured from potatoes, and. when in its natural state, consists of separate grains easily distinguished under the microscope. Upon boiling with wa ter, these grains burst open, and the contents are partially dissolved in the water Upon cooling, it forms a viscid jelly, or rather emulsion, as the starch seems to be more in a state of minute subdivision than in a of solution. When cloth is saturated with it, and pressed with a hot iron, the starch is into gummy substance. which gives the requisite stiffness to the linen. The polished appearance which is sometimes given to starched articles is produced by adding various substances to the starch, among which are gum aratic, gelatine or paraffine. Of the most important article used in the laundry, water, there is little to be said. We may mention, however, that the object of sprinkling dry clothing before ironing is that the steam formed by the heat of the iron may soften the cloth, and allow it to be pressed smooth. It is also to be noted that clothing will dry in the air when the temperature is below freezing as well as on warmer days, thus showing that water evaporates, even when in a frozen condition. - Popular Science NetDS.
 THE NATIONS WEALTH.